High frequency apparatus



March 12, 1940. G, L U ELM N HIGH FREQUENCY APPARATUS Filed Aug. 14,1936 6 Sheets-Sheet 1 INVENTOR G. L. U SSELMAN ATTORNEY March 12, 1940.G, USSELMAN 2,193,500

HIGH FREQUENCY APPARATUS Filed Aug. 14, 1936 6 Sheets-Sheet 2 NEUTRALlZ/N G CONDENSER PREJZfl/RE GAUGE INVENTOR G.L. USSELMAN ATTORN EY March12, 1940. V

ca. L. USSELMAN HIGH FREQUENCY APPARATUS Filed Aug. 14, 1936 6Sheets-Sheet 3 INVEFIITOR e. L. USSELMAN ATTORNEY March 12, 1940. G. L.USSELMAN HIGH FREQUENCY APPARATUS Filed Aug. 14. 1936 I NVENTOR 6Sheets-Sheet 4 G. L. USS ELM'AN ATTORNEY March 12, G L SSELMAN HIGHFREQUENCY APPARATUS Filed Aug. 14, 1936 6 Sheets-Sheet 5 4 I. \V E i r WMarch 1 G. ussELMAN- 2,193,500

area FREQUENCY APPARATUS Filed Aug. 14, 1936 e Sheets-Sheet 6 INVENTORG.L.U$ ELMAN BY ,w'zrm/ ATTORN EY Patented Mar 12, 1940 UNITED suresearner FFECE HIGH FREQUENCY APPARATUS George Lindley Usselm'an, PortJefferson, Y., assignor to Radio Corporation of America, a corporationof Delaware Application August 14, 1936, Serial No. 36,046

6 Claims. (c1.250- ,27) r My present invention relates generally to theimprovement of high frequency apparatus particularly suited for use inshort wave radio transmitters.

Among the objects of my present invention are; I

To provide an improved condenser for high frequency use;

To provide an improved cooling system for vacuum tubes generally;

To provide an improved push-pull arrangement of tubes, tuning andneutralizing condensers, and;

, To provide an improved push-pull vacuum tube arrangement employingcondensers and vacuum tubes, the arrangement being such as to beperfectly symmetrical reactively with respect to tubes and with respectto ground.

A further object of my presentinvention is to provide a neutralizedstage for a radio trans mitter employing neutralizing leads of minimumlength. Such leads are desirable for various reasons and in order toeffect this object I employ condensers of the compressed air or fluidtype. These condensers not only enable me to minimize the length of theneutralizing leads but they also permit optimum utilization of spacewith increased safety factor.

Further objects, advantages, and features of 1111! present inventionwill be apparent as the more detailed description thereof proceeds.

Referring to the drawings which are illustrative'only of my presentinvention;

Figure 1 is a top View of a push-pull stage employing a variable tuningcondenser, parallel vacuum tubes, compressed air neutralizingcondensers, and a fixed auxiliary tuning condenser;

Figure 2 is a view of Figure l takenalong the line 2, 2 of Figure 1;

Figure 3 is a side View of the system shown in Figure 1 andxshows, amongother things, the inductance for the push-pull stage which is made up ofa pair of pipes or fluid conducting tubes, Figure 3 also showing an airvalve for injecting air of desired pressure into one of the neutralizingcondensers and also showing the air gage. for indicating the airpressure and in turn, the

effective capacity of the neutralizing condenser. Generally, the higherthe pressure, the higher the voltage the condenser will stand. Otherfactors for increasing the break-down voltage of the condenser aredescribed and explained hereinafter;

Figures 4, 5, 6, and 7 are side views of concoupling I and shaft 12.

denser plates used in the system shown in Figures 1 and 3; I 'Figure'Bis a rear end view looking from right to left of the system shown inFigures 1 and 3; I

Figures 9 and 10 are views similar to Figures l and 3 of a modifiedpush-pull system employing single tubes rather than parallelled tubes;

Figure 11 is a sectional view through an improved neutralizing condenserwhich may be used in'connection with Figures 1 and 3 01' Figures '9 and10;

Figures 12, 13, and 14 are views of apparatus for uni-controlling orsimultaneously adjusting a pair of neutralizing condensers in a pushpullcircuit.

Turning to Figure 1, the transmitter assembly is set up to include avariable condenser portion to the left, the neutralizing condenser andtube structure at the center, and 'a removable fixed N condenser portionat the right. The entire struc- 2Q ture is generally supported bytwoinsulating strips 2, 4, in turn supported by legs, not shown. or to anysuitable metallic or insulating supporting means.

The variable condenser section is provided with a shaft 6 which rotatesthe variable condenser plates 8 through the medium of a flexible Theflexible coupling I!) is preferably made of the insulating type wherebyshaft 6 may be grounded and whereby 3D shaft l2' is;permitted to float.In this way, the tendency for parasitic oscillation generation isreduced. The rotatable plates 8 are generally supported together with ashaft 22 by means of an insulating strip 14 containing the bearing I6.The general shape of the plates 8 is shown in Figure 2 as is also theshape of the fixed plates i8, 20, the latter being supported upon themetal strips 22, 24, in turn, mounted upon the insulating strips 2, 4respectively.

The central section consists of two metallic blocks 25, 28 supportedupon the metal strips 22.

' 24. The metal blocks 25, 28 generally house and otherwise supportvaccum tubes 3t, 32, 34, and 36, it being noted that tubes 35 and 32 areconnected in parallel as are alsov tubes -34 and 36. Fnese pairs oftubes are connected to the stator plates 18 and 2B, in turn connected tothe op-I posite sides of a push-pull circuit, The neutralizingcondensers 38, All are also connected respectively to the blocks 26, 23but are cross-connected to the pairs of tubesiifi 32 and '34, 36 forneutralization purposes as is known in the art.

The grids of tubes as, 32 are connected to-. gether' by fiat metallicribbon 40' and through lead 42 to the central electrode of neutralizincondenser 413. Similarly, the grids of tubes 34, 36 are connectedtogether by metal ribbon 42 and through lead 44 to the central electrodeof neutralizing condenser 38. As shown in Figure 3, the side view of thearrangement, the grids are also connected to the input leads 46, 48through the conductors 44, 42.

For the longer wavelengths, a fixed condenser section is provided which,as shown in Figures 1 and 3, include condenser plates 50, 52, 54, and5B. Condenser plate 50, with alternate condenser plates 54 and condenserplate 56 are connected to the metal strip 24, in turn connected to theanodes of tubes 3 35 through the metal block 28. Similarly, condenserplate 52, the other alternate plate 54, and condenser plate 58 aresupported by and electrically connected to a metal strip 22. The numberof condenser plates may be varied so as to give the desired capacity.The end plates 56, 52 as shown in Figure 3 and as shown in greaterdetail in Figures 4 and 5 re spectively, are so shaped as to minimizeunbalanced capacity to tubes 26 and 28. By way of xplanation, due todifferences in separation between the tube grids and the condenserplates, the plate 50 offers a greater capacitive reactance to the gridof tube 32 per unit area, than does plate 52 with respect to the grid oftube 36. A0-

. cordingly, if condenser plate 50 were made the same size as condenserplate 54 then its capacity to the grid of tube 32 would be such as tounbalance the push-pull arrangement of tubes, neutralizing condensers,and tuning condensers. Similarly, condenser plate 52 should be made ofsome intermediate size but may be made larger than condenser plate 50 orotherwise, if made too large condenser plate 52 would tend to unbalancethe system by its efiect on the grid of tube 35.

For a somewhat similar reason two end plates 56, 58 are provided whicheliminates unbalance to ground.

The shape of the intermediate plates 54 is shownin Figure 6 and theshape of the end plates 58, 56 is shown in Figure 7.

A rear end view of the condenser assembly is shown in Figured.

The inductance in shunt with the condenser system which includes thevariable and fixed sections as shown in Figure 1, consists of thetubular piping (iii, 62. (Figure 3). Only a section of the pipe 530, 62is shown but it is to be understood that it extends between and iselectrically connected to a pair of inlet and outlet orifices such as64, 66 for block 28. In Figure 3, the inlet and outlet orifices 64, 56are drawn with broken lines. The pipes til, t?! are connected at theirmidpointsto an inlet rubber water pipe, not shown, and an outlet rubberwater pipe, not shown, it being understood that there is ashortcircuiting connection of low impedance across the pipes E9, 52where the rubber pipes are connected. This shortcircuiting strap isslidable along the pipes 6t, '52 which extend parallel. That is to say,the pipes 62 for block 28 and similar pipes 693, 62 for block 2% extendparallel to one another and the short-circuiting strap forms theconnection across both pairs of pipes 62, 62, forming effectivelyU-shaped inductance loop. If desired, the inductance system may becoiled as shown in the patent to H. E. Hall- ,be removed bydisconnecting the straps 68, H! by which it is attached to the framemembers 22, 24.

A further insulating spacer 72?, similar to I4 is provided as shown inFigures 1 and It should be noted in connection with Figure 2 that therotor plates are cut out of a single piece of metal. This form of rotorplatewith two sectors mechanically and electrically connected togetherand as associated with the stator plates 'as shown in Figure l,eliminates objectionable sliding contacts. Sliding contact isobjectionable not only when tuning but also when a tuned condition hasbeen reached and the condenser arrangement shown eliminates theseobjections.

, Figures 9 and 10 are respectively, top and side views of'a modifiedpush-pull system which is generally similar to Figures 1 and 3. inFigures 9 and 10 only a single tube is mounted on each side of thepush-pull system. As shown in Figures 9 and 10, the tubes lfmiilfi andthe neutralizing condensers H34, H36 are alternately arranged at thecorners of a rectangle or a square. The arrangement shown in Figures 9and 10 offers the advantage that the length of the circuit connectionbetween the grid of It will be understood, however, that the areas ofthe respective plates 56,52 and the plate 54 adjacent may be differentlyproportioned from those shown in Figs. 1 and 3, due to the fact that thetubes [0% and I Q2 respectively are not necessarily directly opposed to.one another. The cooling water openings M, 68 of Figure 10 are shownconnected to the doubly wound copper coils I083, I It. Rubber hose inletand outlet pipes H H4 are also provided for each half of the coil, itbeing understood that each half of the coil of Figure 10 goes to eitherblock 26 or block 28.. That is to say, the watercircling through thehose H2 would go to eitherblock 26 or block '28 and the water circlingthrough the rubber hose connection H4 and the other half of thecoilsystem Hi8, Hli' would alsocircle tothe other block, such as, 28 and 26respectively. Also, as

shown in Figure 10, a metal disc orv inductance.

tuner H5 is provided which. is rotated by means of shaft H8 foradditional tuning adjustment.

Returning to Figure 9, an insulating strip I23 is suitably mounted onthe neutralizing condensers IM, 1%. This insulating strip I29 supportsthe grid excitation and neutralizing connections.

The neutralizing condensers referred to hereinabove are described morefully in the copending application of C. W. Hansell, G. L. Usselman,

and C. W. Latimer, Serial No. 27,678, filed June 1935. .That is to say,for high voltage operation I prefer to use the condensers as shown inthis ccpending patent application. For opera" tion at still highervoltages modifications such as shown in Figure 11 are found desirable.In

Figure 11 I have shown a neutralizing condenser which has generalapplication, it being provided with an air inlet l2ll, a pressure gageI24, and

However,

It is to be understood, of course,

For example, the neutralizing con" an outer electrode or wall I26 whichin Figures 1, 3, 9, and 10 is replaced by the metallic blocks 26, 28.The inner electrode structure I23 is adjustable and constructed asdescribed in the copending application referred to. However, to preventcorona creepage along the conical insulator I38 an annular corona shieldI40 at the base of the insulating cone IE8 is provided in order toshield the screw heads I42 for fasten ing the cone i353 to the base I26.Also, a circular doughnut-shaped corona shield M4 is provided at theupper end or apex of the insulating cone I38 which ring shaped coronashield is supported by means of metal arms I46. It has been found thatby the provision of the shields M and I48 the condenser may be subjectedto voltages twice as great as compared to the voltages at which, withoutthe shields, flash-over or arcing takes place between points I42 andI48.

A further feature of my present invention resides in the uni-control ofthe neutralizing condensers shown in Figures 1 and 3 and Figures 9 and10.

Figures 12 and 13 are top and side views ,of uni-control mechanism forsimultaneously ad J'usting the neutralizing condensers I04, I86 whichcorrespond with condensers 33, 4!! shown in Figures l and 3. Referringto Figure 11 when hexagonal nut I50 is rotated the capacity of theneutralizing condenser is altered, as explained more fully in thecopending application of Hansell, Usselman, and Latimer referred tohereinab-ove. The neutralizing condensers 33, 40 of Figures 3., 3, l2,and 13 are provided with these hexagonal adjusting nuts I55 as shownmore clearly in Figure 13. A hexagonal cup, or socket, 152 fits overeach nut I50 and each socket is pinned to a shaft I54. Shafts I54 arepreferably made of insulating material. At the upper end of each shaft,as shown in Figures 12 and 13, there is a 90 worm gear I55 engaging theseparated worm driving gears I58 and lfill. Gears 158, Hill, 164 arepinned or otherwise fastened to the metal drive shaft I66 which isrotated by inserting a screw driver in either of its slotted ends I68,110. A pair of stops I12, I14 are provided which engage a further stopI16. Stop I16 is in the form of a nut threaded to shaft I65 and limitsthe movement of the shaft so as to prevent undesired extreme movementsof the inner electrode of the neutralizing condensers shown in greaterdetail in Figure 11. In order to effect this result the nut I16 is keyedso that it may move axially along the shaft I56 but is prevented by thekeying means, not shown, from rotating with the shaft. Also in order toeffect this result, it should be clear that the socket IE2 is sodimensioned as to permit the nut ifi l to move up and down within thesocket !52 but not rotate within the socket. In other words, the socketI50 and nut I52 rotate together although they are relatively slidablealong the axis of rotation.

figure 14 is a top plan view of a system for simultaneously adjustingthe neutralizing condensers of the arrangement such as shown, forexample, in Figures 9 and 10. Because the condensers are staggered or heon opposite sides of the shaft the gearing 2E0, 262 is similarlystaggered because of corresponding changes in the condenser structure.For this reason, too, the pitch on the sets of gears 25!), is reversed.The mechanism is otherwise similar to that described in connection withFigures 12 and 13 and consequently, further detailed description isbelieved to be unnecessary in view of what has tion of said rotor platesystem from all other portions 'of said apparatus, means for adjustingsaid rotor plate system with respect to said stator plates, a pair ofelectron discharge tubes, each tube having its anode connectedsubstantially directly through connections of low direct current andalternating current resistance and impedance to one of said statorplates respectively, and fixed condenser system connected in shunt tosaid anodes, said fixed condenser system comprising end plates unequallyspaced from said anodes, said end plates being of different size inorderto maintain capacitive symmetry of said tubes with respect to eachother.

2. A push pull system comprising a variable condenser havingcomplementary stator plates disposed in co-planar pairs and acooperating adjustable rotor system comprising plates interleaved withsaid stator plates, a push-pull elec tron discharge tube system thetubes of which have their anodes substantially directly connectedv eachto a particular group of said stator plates, a fixed condenser connectedin shunt with said variable condenser and comprising a plurality ofinterleaved stator plates whereof each plate is of an effective areawhich is a function of its distance away from the electrical center ofsaid discharge tube system, said function being suitably determined forbalancing the electrical characteristics of said tubes, a pair ofneutralizing condensers each having one of its electrodes substantiallydirectly connected to a particular group of said stator plates, andmeans for simultaneously varying the capacities of said neutralizingcondensers.

3. Apparatus of the character described comprising in combination a pairof electron discharge tubes having their anodes disposed in a push-pullarrangement, a tuning condenser systern connected across said anodes andincluding two groups of stator plates and a group of rotor plates,certain of the stator plates of one group being co-planar with respectto corresponding stator plates of the other group, means including aninsulation member for supporting said rotor plates in interleavedrelation to the coplanar stator plates, means including conductivesupports each for electrically interconnecting the stator plates of aparticular group, and for maintaining certain of the same in interleavedrelation to certain of the stator plates of the other group, and meansproviding insulation of all the stator plates of one group from those ofthe other group, said apparatus being further characterized in that astator plate of one group is disposed adjacent the anodes of saiddischarge tubes, said stator plate being of reduced size relative to thestator plate of the other group which is nearest thereto.

4. Apparatus according to claim 3 and further characterized in that twoof the stator plates, one in each group are of progressively diminishedareas relative to others of the interleaved plates, the plate ofsmallest area being disposed nearest the anodes of said discharge tubes.

5. Apparatus according to claim 3 and having two substantially identicalstator plates, one in each group, disposed in a common plane andfurthest removed of all the plates from said discharge tubes.

6. A resonant circuit arrangement for a pushpull system comprising acapacitor having a plurality 01 pairs of co-planar stator plates, andmovable plates interleaved therewith, a set of additional plateselectrically connected to those of the co-planar stator plates which aredisposed v on one side of a plane separating complementary stator platesof each pair, a second set of additional plates electrically connectedwith those of the co-planar stator plates which are disposed on theopposite side of said plane, the plates of said first and second setsbeing interleaved, and a pair of discharge tubes disposed in push-pullrelationship and in unsymmetric proximity to opposing ones of saidadditional plates, certain of said additional plates being ofsufiiciently reduced area with respect to others thereof so thatelectrostatic compensation for said unsymmetric 10 proximity isprovided.

GEORGE LINDLEY USSELMANl

